Description: The purpose of this guide is to describe classification test methods which may be used to compare insulation systems in use, or proposed for use, in large high-voltage rotating machines. The tests are applicable to the insulation systems used in coils of generators, motors, and synchronous condensers operating at 6600 V and above. The basic ingredient of these insulation systems is usually mica combined with reinforcing, bonding, and impregnating materials. This guide is based on the experience of the industry with micaceous systems; any evaluation of nonmicaceous systems should, however, consider the requirements of this guide.